One of the more annoying things about politics is that you can swing from left to right, or vice versa, without ever changing positions.

For instance, in 2002, I came in favor of same-sex domestic partnerships, or "civil unions." This was widely seen as a compromise between advocates of gay marriage and opponents. It would offer all the rights and benefits of marriage while still reserving the institution of marriage itself for heterosexual couples.

It's probably hard for young people to appreciate today, but back then, that was a very left-wing thing for someone to do. And for a conservative like yours truly, it was a kind of apostasy. Various social conservatives attacked me. But within a few years, the zeitgeist moved dramatically on the issue. Denying gays the last benefit of marriage -- the word itself -- was bigotry and "right-wing extremism."

In other words, I didn't move, the ground underneath me did.

This is an old story in politics. Ronald Reagan used to say he never left the Democratic Party, the Democratic Party left him.

Sometimes the parties don't change sides. Rather, one party moves much further in one direction, moving the center of gravity between the two parties with it.

Reagan did this on economics. Prior to Reagan, both parties were essentially liberal on the role of government in the economy. Richard Nixon bragged that his administration was the first to spend as much on domestic programs as on defense. He created the EPA, imposed wage and price controls, and was a modest protectionist on trade. The Democrats were to his left, for the most part, though not far to his left.

But Reagan moved the GOP to the libertarian "right," championing less regulation, lower taxes and freer markets. His success caused the Democrats to eventually (and, alas, briefly) move in his direction under Bill Clinton.

If you're invested in a particular position, it can be disorienting to live through one of these moments. Tectonic plates are always moving, and when they move suddenly, not only does the ground under your feet move, lots of things come crashing down.

You might have noticed we're living in one of these moments.

For decades, conservatives extolled the FBI and intelligence agencies as some of the only branches of government worthy of veneration, while liberals saw them as the only parts of big government deserving of distrust and skepticism. But partisanship is a hell of a drug, and now the loudest conservatives are denouncing the incompetence, corruption and abuses of the "Deep State," while the loudest liberals are shocked -- shocked! -- that anyone would question the integrity of these patriotic guardians of our liberty and safety.

My National Review colleague Kevin Williamson recently wrote an interesting essay on how liberals might become the new champions of free trade thanks to Donald Trump's steering of the GOP toward protectionism. Liberals -- particularly when the label still had some of its original spirit to it -- were once the champions of free trade. Republicans were less interested in the free market and more interested in helping big businesses that didn't want competition from abroad. I remain skeptical about this shift -- and so is Williamson -- but one could imagine scenarios where it could happen.

Immigration -- to my mind the single biggest driver of the populist tumult overtaking our politics -- is marked by a slightly different dynamic. Just as the Reagan-era GOP moved the political center to the right, the Obama-era Democrats moved -- lurched, really -- to the left on immigration. Famous liberals such as Bill Clinton, Barack Obama, Paul Krugman and Bernie Sanders have said things in the recent past about illegal immigration that would mark them as "right-wing" today.

This might not be obvious for two reasons. First, because of the mainstream media's alignment with the Democrats, it has a hard time noticing when Democrats are the "extremists" in any debate. Extremism is a Republican thing.

Second, Trump's rhetoric on immigration has indeed been extreme. From his Muslim ban, to describing Mexican immigrants as "rapists," to his comment about "s---hole countries," he says things (and may want things) that are objectively extreme. But Trump's actual policy proposal isn't nearly as extreme as what comes out of his mouth. In the State of the Union address, he offered a sweeping amnesty for millions of illegal immigrants in exchange for, among other things, a border wall Democrats at least rhetorically supported a few years ago.

I have no idea how it will all shake out, because you can't survey the damage from an earthquake until the shaking stops.